The disclosure relates to a transmission arrangement, a travel drive with transmission arrangement, as well as a method for controlling the transmission arrangement.
Publication DE 10 2005 058 937 A1 shows a generic travel drive. Therein, a hydrostatic transmission is coupled on one hand to a drive machine and a downstream manual transmission is coupled on the other hand to an output drive. The manual transmission is provided for extending a speed range of the travel drive in comparison with a travel drive with a purely hydrostatic transmission.
In order to be able to perform a transmission stage change in the manual transmission, the manual transmission should be approximately load-free during release of an engaged transmission stage. In other words, the torque acting between the hydrostatic transmission and the manual transmission must be approximately zero. This is ensured in the case of the solution shown via a reduction in the displacement volume of the hydraulic motor. In this torque-free state, the old transmission stage is then disengaged and the new transmission stage can be engaged via a mechanical, friction-based synchronization. The shifting process can be carried during travel or during interruption of travel, i.e. at a standstill.
Publication DE 10 2004 061 558 A1 also shows a generic travel drive in the case of which the manual transmission can be shifted in a similar manner during travel or at a standstill. In the case of the latter solution, it is furthermore proposed to use the reduction in the displacement volume of the hydraulic motor, i.e. the reduction in torque of the hydraulic motor, not only to support the transmission stage change, but also to improve a braking operation. A braking signal is detected by a control unit and, as a result, the displacement volume of the hydraulic motor is reduced to a minimum value. The output shaft of the hydraulic motor is then torque-free and the service brake only has to brake the kinetic energy of the free-rolling vehicle since no drive power of the hydraulic motor which counteracts the braking power is present.
It is disadvantageous in known solutions that, in the case of standstill, a shift release is only carried out as a function of a transmission output rotational speed, namely if this is zero. Although the vehicle is stationary, the vehicle can, however, be accelerated unintentionally under certain ambient conditions (wind, downhill forces) during release of the engaged transmission stages, as a result of which damage to the transmission and even endangering of the vehicle, its occupants and the surroundings are possible.
Against this background, the object on which the disclosure is based is to create a transmission arrangement via which secure shifting at a standstill is enabled. The object furthermore lies in creating a travel drive with such a transmission arrangement and a method for controlling this transmission arrangement.